The present invention relates to a sleeve for loading pellets, such as catalyst pellets, into chemical reactor tubes. Typically, the chemical reactor tubes are vertically arranged tubes which are held together by one or more tube sheets to form the basic structure of some chemical reactors. One tube sheet is generally located near the top of the reactor, with the reactor tubes extending downwardly from it. Additional tube sheets may be located near the bottom or middle of the tubes. References to the tube sheet herein generally relate to the upper tube sheet. The reactor tubes often are loaded with catalyst pellets, which assist in the chemical reaction. In order for the reactor to perform optimally, it usually is desirable to distribute the catalyst pellets evenly in the tubes.
When loading the tubes of a reactor vessel, the catalyst pellets may be very abrasive and may have a very strong tendency to bridge across the tube, stopping the further flow of pellets through the tube. It is desirable to load the catalyst pellets into the reactor vessel tubes at a controlled rate to eliminate bridging and to ensure uniform packing of the pellets within the tubes of the reactor vessel. Ideally, this controlled rate is such that the number of pellets simultaneously passing through any point is fewer than the number of pellets required to form a bridge. The rate usually is controlled by controlling the size of the opening through which the pellets pass into the reactor tube.
In typical loading procedures, the reactor tubes are filled to the top with catalyst, and then the catalyst is vacuumed out to the desired “outage” level, with the “outage” being the empty space within the reactor tube above the catalyst. This process is labor intensive and tends to degrade the catalyst, so it would be desirable to be able to load the catalyst pellets directly to a required “outage” level, such that pellets do not have to be vacuumed out or added after the loading in order to reach the desired outage level.
Sometimes, long loading sleeves are used so that, when the sleeve is filled and then is removed, the catalyst pellets fall to the desired height or outage. However, there often are problems with catalyst bridging in the sleeve as the sleeve is being removed, and there may be height limitations within the reactor which prevent the use of long loading sleeves.